Rework internal rpc protocol handling (#4290)

## Issue Addressed

Resolves #3980. Builds on work by @GeemoCandama in #4084 

## Proposed Changes

Extends the `SupportedProtocol` abstraction added in Geemo's PR and attempts to fix internal versioning of requests that are mentioned in this comment https://github.com/sigp/lighthouse/pull/4084#issuecomment-1496380033 

Co-authored-by: geemo <geemo@tutanota.com>

beacon_node/lighthouse_network/src/rpc/methods.rs

@@ -3,11 +3,13 @@
 use crate::types::{EnrAttestationBitfield, EnrSyncCommitteeBitfield};
 use regex::bytes::Regex;
 use serde::Serialize;
+use ssz::Encode;
 use ssz_derive::{Decode, Encode};
 use ssz_types::{
     typenum::{U1024, U256},
     VariableList,
 };
+use std::marker::PhantomData;
 use std::ops::Deref;
 use std::sync::Arc;
 use strum::IntoStaticStr;
@@ -85,6 +87,30 @@ pub struct Ping {
     pub data: u64,
 }
 
+/// The METADATA request structure.
+#[superstruct(
+    variants(V1, V2),
+    variant_attributes(derive(Clone, Debug, PartialEq, Serialize),)
+)]
+#[derive(Clone, Debug, PartialEq)]
+pub struct MetadataRequest<T: EthSpec> {
+    _phantom_data: PhantomData<T>,
+}
+
+impl<T: EthSpec> MetadataRequest<T> {
+    pub fn new_v1() -> Self {
+        Self::V1(MetadataRequestV1 {
+            _phantom_data: PhantomData,
+        })
+    }
+
+    pub fn new_v2() -> Self {
+        Self::V2(MetadataRequestV2 {
+            _phantom_data: PhantomData,
+        })
+    }
+}
+
 /// The METADATA response structure.
 #[superstruct(
     variants(V1, V2),
@@ -93,9 +119,8 @@ pub struct Ping {
         serde(bound = "T: EthSpec", deny_unknown_fields),
     )
 )]
-#[derive(Clone, Debug, PartialEq, Serialize, Encode)]
+#[derive(Clone, Debug, PartialEq, Serialize)]
 #[serde(bound = "T: EthSpec")]
-#[ssz(enum_behaviour = "transparent")]
 pub struct MetaData<T: EthSpec> {
     /// A sequential counter indicating when data gets modified.
     pub seq_number: u64,
@@ -106,6 +131,38 @@ pub struct MetaData<T: EthSpec> {
     pub syncnets: EnrSyncCommitteeBitfield<T>,
 }
 
+impl<T: EthSpec> MetaData<T> {
+    /// Returns a V1 MetaData response from self.
+    pub fn metadata_v1(&self) -> Self {
+        match self {
+            md @ MetaData::V1(_) => md.clone(),
+            MetaData::V2(metadata) => MetaData::V1(MetaDataV1 {
+                seq_number: metadata.seq_number,
+                attnets: metadata.attnets.clone(),
+            }),
+        }
+    }
+
+    /// Returns a V2 MetaData response from self by filling unavailable fields with default.
+    pub fn metadata_v2(&self) -> Self {
+        match self {
+            MetaData::V1(metadata) => MetaData::V2(MetaDataV2 {
+                seq_number: metadata.seq_number,
+                attnets: metadata.attnets.clone(),
+                syncnets: Default::default(),
+            }),
+            md @ MetaData::V2(_) => md.clone(),
+        }
+    }
+
+    pub fn as_ssz_bytes(&self) -> Vec<u8> {
+        match self {
+            MetaData::V1(md) => md.as_ssz_bytes(),
+            MetaData::V2(md) => md.as_ssz_bytes(),
+        }
+    }
+}
+
 /// The reason given for a `Goodbye` message.
 ///
 /// Note: any unknown `u64::into(n)` will resolve to `Goodbye::Unknown` for any unknown `n`,
@@ -197,7 +254,11 @@ impl ssz::Decode for GoodbyeReason {
 }
 
 /// Request a number of beacon block roots from a peer.
-#[derive(Encode, Decode, Clone, Debug, PartialEq)]
+#[superstruct(
+    variants(V1, V2),
+    variant_attributes(derive(Encode, Decode, Clone, Debug, PartialEq))
+)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct BlocksByRangeRequest {
     /// The starting slot to request blocks.
     pub start_slot: u64,
@@ -206,8 +267,23 @@ pub struct BlocksByRangeRequest {
     pub count: u64,
 }
 
+impl BlocksByRangeRequest {
+    /// The default request is V2
+    pub fn new(start_slot: u64, count: u64) -> Self {
+        Self::V2(BlocksByRangeRequestV2 { start_slot, count })
+    }
+
+    pub fn new_v1(start_slot: u64, count: u64) -> Self {
+        Self::V1(BlocksByRangeRequestV1 { start_slot, count })
+    }
+}
+
 /// Request a number of beacon block roots from a peer.
-#[derive(Encode, Decode, Clone, Debug, PartialEq)]
+#[superstruct(
+    variants(V1, V2),
+    variant_attributes(derive(Encode, Decode, Clone, Debug, PartialEq))
+)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct OldBlocksByRangeRequest {
     /// The starting slot to request blocks.
     pub start_slot: u64,
@@ -223,13 +299,43 @@ pub struct OldBlocksByRangeRequest {
     pub step: u64,
 }
 
+impl OldBlocksByRangeRequest {
+    /// The default request is V2
+    pub fn new(start_slot: u64, count: u64, step: u64) -> Self {
+        Self::V2(OldBlocksByRangeRequestV2 {
+            start_slot,
+            count,
+            step,
+        })
+    }
+
+    pub fn new_v1(start_slot: u64, count: u64, step: u64) -> Self {
+        Self::V1(OldBlocksByRangeRequestV1 {
+            start_slot,
+            count,
+            step,
+        })
+    }
+}
+
 /// Request a number of beacon block bodies from a peer.
+#[superstruct(variants(V1, V2), variant_attributes(derive(Clone, Debug, PartialEq)))]
 #[derive(Clone, Debug, PartialEq)]
 pub struct BlocksByRootRequest {
     /// The list of beacon block bodies being requested.
     pub block_roots: VariableList<Hash256, MaxRequestBlocks>,
 }
 
+impl BlocksByRootRequest {
+    pub fn new(block_roots: VariableList<Hash256, MaxRequestBlocks>) -> Self {
+        Self::V2(BlocksByRootRequestV2 { block_roots })
+    }
+
+    pub fn new_v1(block_roots: VariableList<Hash256, MaxRequestBlocks>) -> Self {
+        Self::V1(BlocksByRootRequestV1 { block_roots })
+    }
+}
+
 /* RPC Handling and Grouping */
 // Collection of enums and structs used by the Codecs to encode/decode RPC messages
 
@@ -438,7 +544,12 @@ impl std::fmt::Display for GoodbyeReason {
 
 impl std::fmt::Display for BlocksByRangeRequest {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "Start Slot: {}, Count: {}", self.start_slot, self.count)
+        write!(
+            f,
+            "Start Slot: {}, Count: {}",
+            self.start_slot(),
+            self.count()
+        )
     }
 }
 
@@ -447,7 +558,9 @@ impl std::fmt::Display for OldBlocksByRangeRequest {
         write!(
             f,
             "Start Slot: {}, Count: {}, Step: {}",
-            self.start_slot, self.count, self.step
+            self.start_slot(),
+            self.count(),
+            self.step()
         )
     }
 }